Evaluation of the repeatability and reliability of the cross-training specific Fight Gone Bad workout and its relation to aerobic fitness

Cross-training is a high-intensity functional training (HIFT) with multiple workout modalities. Despite the increasing number of studies in HIFT, there is still no validated test to measure its specific performance. It would also be advisable to determine whether selected cross-training workouts can implement a stimulus corresponding to maximize aerobic work. For these reasons, the purpose of our study was to evaluate the repeatability and reliability of Fight Gone Bad (FGB) workout and to assess its relationship with aerobic fitness. Twenty-one cross-training participants (9 females) finished the study protocol which included three two-day measurement sessions separated by 10 days. During each session, participants had their body composition measured, and they performed two exercise tests. The first test was an incremental cycling test to measure aerobic fitness, and the second was a cross-training specific FGB workout performed the next day. Reliability and repeatability were calculated from the three measurements. The total FGB Score (FGB(TOTAL)) showed excellent reliability (ICC 0.9, SEM 6%). Moreover, FGB(TOTAL) was strongly correlated with aerobic fitness (i.e., time to exhaustion (T(exh), R(2) = 0.72), maximal workload (W(max), R(2) = 0.69), time to gas exchange threshold (T(GET), R(2) = 0.68), and peak oxygen uptake (VO(2peak), R(2) = 0.59). We also found that agreement between standardized FGB and standardized aerobic performance indices such as T(exh), VO(2peak), W(max), maximum heart rate, T(GET), and workload at gas exchange threshold was high by the Bland–Altman method. In conclusion, FGB is a reliable test that can be used in order to measure changes in cross-training performance caused by an intervention. Moreover, FGB is strongly correlated to aerobic fitness.